Elections are audited as a matter of course. In California every election is audited after the fact, in addition to observers (including from the different parties) wherever voting, tabulating, and auditing occurs. Here's the bill of rights for election observers:
https://www.sos.ca.gov/administration/regulations/current-re... They have access to everything.
Claims of fraud generally come from either people who have no experience with elections (and apparently don't care enough to get involved), or wish to sow uncertainty and doubt in their self-interest.
Sometimes auditors make complaints, but those complaints are a far cry from the accusations thrown around in public discourse. More often election officials themselves make recommendations to improve things--usually efficiency related--but the discourse is so heated legislatures often don't want to get involved, or if they do it's to appease some political faction, not to address the mundane issues that actually need addressing.
If you're so worried about election fraud, get involved. There aren't any barriers. Heck, in some places you can easily volunteer to host a voting place. Some years we get flyers to ask if we want to host, but usually the only house on our block who offers is the same one down the block.
What I don't get is the conspiratorial minded folks who make accusations, but demand other people fix whatever imagined problem exists. How can you trust the new system any more if you're still a keyboard warrior? It makes no sense. The public is locked out of direct involvement with most machinations of governance, but elections are one of the few areas where you're free to get involved at almost every level with minimal, even zero friction.